The variety of sounds and range of amplitudes which can be produced with a traditional musical instrument are circumscribed by its design and by the physical limitations of the musician. Most conventional harmonicas, for example, are tuned to play a very limited range of full tones and cannot produce sharp or flat half tones. An experienced player can "bend" the notes to approximate half tones, but the result is less than desirable. The volume or amplitude of the tones produced by a conventional harmonica is also limited by the lung capacity of the musician.
Mechanically modified harmonicas have been designed to enable generation of half tones, as well as full tones. U.S. Pat. No. 2,565,100, issued Aug. 21, 1951 to J. R. Tate, discloses one example. Such instruments typically require the player learn new lip and hand movements that differ substantially from conventional techniques for playing a harmonica. These prior art instruments are also incapable of providing for other embellishments that would be desirable, such as adding chords or octave notes or changing frequencies, key, scale tempo or the like.
Prior efforts to increase the range of sound intensities obtainable from a harmonica have included installation of a microphone on the harmonica which is coupled to a loudspeaker through an electrical amplifier, as exemplified by the above identified U.S. Pat. No. 2,565,100. This results in the production of the music at the harmonica itself accompanied by a reproduction of the music at the loudspeaker location. Feedback effects, in such an arrangement, can disturb the musical performance. Such a system also does not enable any embellishments of the music produced by the harmonica, other than volume amplification.
Recent developments in electronic sound synthesizers have overcome the limitations imposed by the design of traditional musical instruments and by the physical capabilities of the musician. Such systems, in the most advanced forms, are typically controlled by a digital microprocessor be actuated with a keyboard or other input device, to produce virtually any audible tone and to provide any of a great variety of embellishments.
A harmonica construction capable of controlling such synthesizers significantly enhances the range of musical options available to harmonica players. Preferably such an instrument should have the feel of the traditional instrument and not require any substantial alteration of the conventional techniques for playing a harmonica.
Prior efforts to dispense with the reeds in the conventional harmonica and to substitute electrical elements for controlling an electrical sound producing device have not extended the capabilities of the conventional instruments.
U.S Pat. No. 2,455,032, issued Nov. 30, 1948 to A. 0. Williams, describes a construction in which the reeds are replaced with pressure sensitive switches, each of which can be operated by blowing into the harmonica and each of which causes a tone generator to produce a different one of a series of predetermined audio frequencies. The switches are on-off devices which cannot detect variations in the amplitude of notes that a musician generates.
U.S. Pat. No. 3,516,320, issued June 23, 1970 to C. A. Hillairet et al., also teaches the use of a series of air flow actuated switches to detect air flow in any of the passages of a harmonica. Actuation of any of the switches changes the output frequency of an electrical oscillator, which is coupled to an audio speaker through an amplifier, to produce the musical note which corresponds to the particular air passage. The circuit is an improvement of the Williams device in that an air velocity detector modulates the amplifier gain to vary the volume of the generated sound in response to variations in the flow rate of the player's breath. Additional controls enable the player to shift octaves and to introduce effects such as tremolo and production of semi-tones.
However, the apparatus of U.S. Pat. No. 3,516,320 does not generate separate electrical signals for each air passage that are independent of each other and which encode both activation of the passage by the musician and also the desired amplitude of the note. The note sensing switches are interlinked at the single oscillator which cannot respond accurately to simultaneous actuation of more than one such switch. The separate amplitude detecting means is a single detector which jointly monitors all air passages. These characteristics do not provide the necessary versatility for controlling a sound synthesizer.
A further characteristic of prior electronic harmonicas is undesirable mechanical complexity and fragility in the air flow sensing mechanisms. This makes such instruments costly and prone to malfunction from the effects of saliva, dust, impacts or the like.
The present invention is directed to overcoming one or more of the problems discussed above.